A misting system converts a fluid, typically water, into a mist or fog. One of the primary uses of such a system is to cool the proximate area. Such cooling takes place by evaporation of the mist or fog. The efficiency of evaporation, hence the efficiency of cooling, is a function of droplet size. The smaller the droplet, the more rapid its evaporation and the greater the cooling efficiency. A type of mist more precisely considered to be a fog is preferable to a mist having larger droplets.
A misting system has one or more misting heads, which perform the actual conversion of the fluid into a mist or fog. In order to accomplish this, the misting head fractures the water, i.e., disrupts molecular cohesion. The fluid enters the misting head under pressure. A fluid moving under pressure pulsates. This pulsation is due in part to air entrained within the fluid, and in part to turbulence created by friction and other factors.
The pulsating fluid exits the misting head through an orifice. This orifice serves to fracture the fluid into a fine spray. Usually, this fracturing is insufficient to produce the desired mist or fog, and further fracturing is desirable.
This further fracturing is typically provided by the addition of a poppet to the misting head. The misting head is formed with a cylindrical chamber within which the poppet resides. The pulsation of the fluid causes the poppet to vibrate within the chamber and fracture the fluid. This fractured fluid then exits the misting head through the orifice and undergoes further fracturing. This compound fracturing action improves the quality of atomization compared to systems that do not employ compound fracturing.
A problem occurs in that the poppet may occasionally seat against the orifice in such a manner that the flow is cut off. Should this occur, the fluid pressure may serve to hold the poppet in this position. In conventional misting heads, this problem is solved by cutting one or more small blind slits in the orifice end of the poppet. These slits serve to prevent a perfect seal from forming between the end of the poppet and the orifice. Without such a seal, the fluid vibration serves to prevent the poppet from remaining in this position. Also, these slits cause the poppet to spin. This spin serves to increase the vibration of the poppet. This increased vibration increases the fracturing of the fluid. Additionally, the edges of the slits themselves create an additional turbulence of the fluid. This additional turbulence again increases the fracturing action.
The poppet must be smaller in diameter than the chamber in which it resides. This allows the poppet to spin and vibrate within the chamber and allows fluid to pass by the poppet within the chamber. A problem exists, however, in that the poppet may undergo a certain amount of lateral movement within the chamber. This lateral movement varies the space between the poppet and the chamber wall in a totally random manner. This in turn produces random variations in the pressure present at the orifice, hence the degree of fracture produced by the orifice. This may result in spitting, dribbling, or other undesirable output from the misting head.
Additionally, the poppet may become skewed and wedge within the chamber. This is accompanied by a significant decrease in the amount of fracture and an undesirable degradation of the output from the misting head.
What is desirable, therefore, is a way of keeping a poppet centered within a misting head chamber and controlling lateral poppet movement. This would in turn maintain a controlled pressure at the orifice, a controlled fracture, and a controlled misting head output.
Even with the fracture slits, a problem also remains in that the pressure must be relatively high to produce a smaller droplet fog rather than a larger droplet type of mist. This high pressure is reflected in more robust piping and other components, including the misting heads themselves.
What is desirable, therefore, is a way of increasing the amount of fracture, thus producing a given fog output at a lower pressure. This in turn would allow a decrease in component robustness for a given amount of mist, with a corresponding decrease in system cost and complexity.